The growing demand in portable and compact consumer devices and appliances has resulted in the need for the miniaturisation of electronic components. These miniaturised electronic components are sensitive and susceptible to damage by voltages as low as 20V. Electrically conductive styrenic thermoplastics are widely used in electronic packaging applications to protect these sensitive electronic components against electro-static discharge (ESD) during manufacturing, assembly, storage and shipping. Such ESD applications often require the optimal volume resistance range of ≥ 1.0x105 to < 1.0x108 Ω. The best known method to render styrenic thermoplastics conductive is by the incorporation of conductive fillers, such as carbon black but the main limitation is the difficulty in controlling the conductivity level due to the steep percolation curve. Thus the aim of this research is to develop electrically conductive styrenic thermoplastics by blending several styrenic resins with polymeric conductive additives to achieve optimal volume resistance range for ESD applications with the ease in controlling the conductivity level.

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Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: This work involves the study of the effects of Reversible Addition-Fragmentation Chain Transfer (RAFT) agents on the emulsion polymerization of styrene. The feasibility of RAFT as a method for obtaining controlled radical polymerizations in emulsion systems is also investigated. Both seeded and ab initio systems were studied with three RAFT agents of varying structure. Inhibition and retardation effects on addition of various amounts of the RAFT agents to the emulsion systems were observed and the trends noticed. The effect of the RAFT agents on the average number of radicals per latex particle was calculated from reaction rates. The effect of the RAFT agent on the molecular weight and the molecular weight distribution was monitored by gel permeation chromatography. Exit of free radicals from the latex particles proves to be a major feature in the studied RAFT emulsion systems. Fragmentation of the RAFT agent in the latex particles, gives rise to free radical species that can exit from the particle and enter other particles where they can either terminate instantaneously or propagate. The exit and termination processes presumably result in both the inhibition and retardation of the emulsion polymerizations. A linear increase in Mn with conversion is observed, however the low concentration of RAFT agent in the latex particles is responsible for the obtained number average molecular weights being much higher than predicted. The low concentrations of RAFT agents in the latex particles is also responsible for the broad molecular weight distributions that are obtained. Reaction conditions for RAFT experiments should to be chosen so that the effects of exit processes are minimized and that the RAFT agent is primarily situated in the latex particles. These conditions must be met if the RAFT process is to be successful as a method of controlled radical polymerization in emulsions. / AFRIKAANSE OPSOMMING: Hierdie navorsing behels die studie van die effek van In bygevoegde addisie-fragmentasie kettingsoordragsreagent (RAFT1) op die emulsie polimerisasie van stireen. Die uitvoerbaarheid van RAFT as 'n metode om gekontroleerde radikale polimerisasies in emulsiesisteme te verkry is ook ondersoek. Eksperimente met drie RAFTkettingoordragsreagente van gevarieerde strukture is uitgevoer in beide seeded en ab initia sisteme. Die effek van die RAFT-reagent op die inhibisie en vertraging van die emulsie polimerisasie is waargeneem en die invloed van RAFT op die gemiddelde aantal radikale per partikel is bepaal. Die ontwikkeling van die molekulêre massa en die molekulêre massadistribusie is waargeneem deur middel van gel permeasie- kromatografiese tegnieke. Die ontsnapping van vrye radikale vanuit die partikels was 'n belangrike faktor in RAFT emulsiesisteme wat ondersoek is. Hierdie radikale is gegenereer deur die fragmentasie van die oorspronklike RAFT-reagent. Fragmentasie van die RAFT-reagent in die lateks partikels lei tot die vorming van vrye radikale spesies wat uit een partikel kan ontsnap en ander partikels kan binnedring waar dit onmiddellik kan termineer of propageer. Die ontsnappings- en terminasieprosesse van vrye radikale lei oënskynlik tot die inhibering en vertraging van die emulsie polimerisasie. 'n Lineêre verhoging in die gemiddelde molekulêre massa tydens konversie is waargeneem, alhoewel die Mn-waardes baie hoër was as wat verwag is. Die verskil kan toegeskryf word aan die klein hoeveelhede van die RAFT-reagent wat in die partikels teenwoordig is. Hierdie lae RAFT-konsentrasies is ook verantwoordelik vir die breë molekulêre massa distribusie wat waargeneem is. Vir die RAFT-proses om suksesvol te wees in gekontroleerde radikale polimerisasies in emulsies, moet reaksie kondisies so gekies word dat die ontsnapping van vrye radikale tot 'n minimum beperk word en die RAFT-reagent hoofsaaklik in die lateks partikels teenwoordig is.

Waste plastic treatment was a global issue currently. A sustainable recycling process was required to recovery the monomer units from the polymer, thus avoiding environmental impacts due to disposal and enhancing the economic benefit from the recovered products. Pyrolysis was one of the promising process and previous MQP group has studied the pyrolysis with molten salts. In this work, a standardized and optimized pyrolysis reaction process of polystyrene was developed, based on the previous work on molten salt pyrolysis 5. The literature of pyrolysis mechanism and catalytic effects were reviewed as a guide process design. The orientation of the reactor was standardized to be consistent with literature record of preceding work. The positioning of the flow tube for the carrier gas and thermocouple were standardized in locations to provide mixing process of the reactant, the removal of products, and the accurate measurement of reaction temperature. The product collection system was also investigated and optimized to maximize collection efficiency while avoiding excessively low temperatures. The experiment results with standardized reaction configuration showed an improved styrene yield, 65%, compared with a previous yield of 44%. Then with the standardized reaction configuration, the catalytic effects of molten salt were studied at 400℃ pyrolysis temperature. Quantitative analysis indicated that the molten salt improved the styrene selectivity of the monomer compared to the dimer. Analysis of product composition and mass balance indicated formation of heavy non-GC detectable species in the liquid products. Gas phase secondary reaction during pyrolysis, and re-polymerization inside the liquid products, were discussed to explain the different styrene yield and the existence of heavy species. Based on the current results, recommendations for the pyrolysis temperature, initial reactants loading, and condenser temperature and analysis strategies were provided for further study of the molten salt pyrolysis of polystyrene.

Thesis (M.Sc. (Chemistry)) --University of Limpopo, 2014 / This study deals with the synthesis and characterisation of cobalt complexes of nitrogen-donor imidazolyl- salicylaldimine ligands and their potential catalytic activity in the oxidation reactions of phenol and styrene. Five ligands were used in the study, four of which are new. Compound 2,4-di-tert-butyl-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L1), was synthesised according to a literature procedure. The other imidazole-based salicylaldimine compounds 2-ethoxy-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L2), 4-methoxy-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L3), 1{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-benzene (L4) and 4-methyl-1{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-benzene (L5) were prepared by Schiff base condensation reaction of histamine dihydrochloride with 3-ethoxy-2-hydroxybenzaldehyde, 5-methoxy-2-hydroxybenzaldehyde, benzaldehyde, 4-methylbenzaldehyde respectively. L1-L5 were characterised by 1H and 13C{1H} NMR, IR and UV-vis spectroscopy and high resolution mass spectrometry (HRMS). Reactions of L1-L5 with CoCl2 yielded complexes C1-C5, while complexes C6-C10 were synthesised by reactions of L1-L5 with CoBr2 all in a ratio of 1:1 of ligand to metal precursor. The cobalt(II) complexes were characterised by IR and UV-vis spectroscopy, elemental analysis and high resolution mass spectrometry due to their paramagnetic nature. All the characterisation data point to complexes C1-C10 being formulated as [Co(3-L)X] (where L = ligand and X = halide). However, single crystal X-ray diffraction showed that the prolonged stay of complex C6 in a solution gave a new structure as complex C11. The imidazole-based salicylaldimine cobalt(II) complexes (C1-C10) were tested as catalysts for the oxidation reactions of phenol and styrene with H2O2, O2 and 3-chloroperbenzoic acid as oxidants. The complexes were found not to be active for the oxidation of both substrates (phenol and styrene) with 0% conversion, even when the reactions were left for 1 week. Analysis of the oxidation reactions were performed with GC and 1H NMR spectroscopy. Both analysis methods showed the presence of unreacted substrates at the end of the reaction period. Effects of concentration of pre-catalysts, substrates and oxidants, time and temperature of reaction and nature of solvent on catalytic activity were also investigated, however the conversions remained at 0% conversion. / Sasol Inzalo Foundation

Thesis (MSc. (Chemistry)) --University of Limpopo, 2014 / This study deals with the synthesis and characterisation of cobalt complexes of nitrogen-donor imidazolyl- salicylaldimine ligands and their potential catalytic activity in the oxidation reactions of phenol and styrene. Five ligands were used in the study, four of which are new. Compound 2,4-di-tert-butyl-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L1), was synthesised according to a literature procedure. The other imidazole-based salicylaldimine compounds 2-ethoxy-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L2), 4-methoxy-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L3), 1{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-benzene (L4) and 4-methyl-1{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-benzene (L5) were prepared by Schiff base condensation reaction of histamine dihydrochloride with 3-ethoxy-2-hydroxybenzaldehyde, 5-methoxy-2-hydroxybenzaldehyde, benzaldehyde, 4-methylbenzaldehyde respectively. L1-L5 were characterised by 1H and 13C{1H} NMR, IR and UV-vis spectroscopy and high resolution mass spectrometry (HRMS). Reactions of L1-L5 with CoCl2 yielded complexes C1-C5, while complexes C6-C10 were synthesised by reactions of L1-L5 with CoBr2 all in a ratio of 1:1 of ligand to metal precursor. The cobalt(II) complexes were characterised by IR and UV-vis spectroscopy, elemental analysis and high resolution mass spectrometry due to their paramagnetic nature. All the characterisation data point to complexes C1-C10 being formulated as [Co(3-L)X] (where L = ligand and X = halide). However, single crystal X-ray diffraction showed that the prolonged stay of complex C6 in a solution gave a new structure as complex C11. The imidazole-based salicylaldimine cobalt(II) complexes (C1-C10) were tested as catalysts for the oxidation reactions of phenol and styrene with H2O2, O2 and 3-chloroperbenzoic acid as oxidants. The complexes were found not to be active for the oxidation of both substrates (phenol and styrene) with 0% conversion, even when the reactions were left for 1 week. Analysis of the oxidation reactions were performed with GC and 1H NMR spectroscopy. Both analysis methods showed the presence of unreacted substrates at the end of the reaction period. Effects of concentration of pre-catalysts, substrates and oxidants, time and temperature of reaction and nature of solvent on catalytic activity were also investigated, however the conversions remained at 0% conversion.

This thesis presents the results of a study on the kinetics of nitroxide-mediated radical polymerization of styrene with a unimolecular initiator. The primary objective was to obtain a more comprehensive understanding of how a unimolecular-initiating system controls the polymerization process and to clarify the effects of various reaction parameters. Previous work in this field has met with some difficulties in the initiator synthesis, such as low yield and inconsistency of molecular weight. These problems were overcome by adjusting reaction conditions and procedures. Better yields of initiator with consistent molecular weight were produced by the improved methods. Control of polymerization rate and polymer molecular weight in unimolecular nitroxide-mediated radical polymerization was studied by looking at the effects of the three main factors: initiator concentration, temperature, and the initiator molecular weight on polymerization rate, molecular weight and polydispersity. Results indicated that increasing the initiator concentration had no effect on polymerization rate at low conversion, but led to lower polymerization rate at high conversion; higher initiator concentration led to lower molecular weight of the resulting polymer. It was also found that temperature significantly increased the polymerization rate, yet had no effect on number-average molecular weight, Mn, at low conversion, while it caused a plateau at high conversion levels; there was no effect on weight-average molecular weight, Mw, through the whole conversion range. In addition, increasing initiator molecular weight was found to have no effect on either polymerization rate or molecular weight. The experimental molecular weights of the unimolecular system were compared to theoretical molecular weights based on ideal controlled radical polymerization (CRP). The results were found to be close to the theoretical values. This confirmed the advantages of the unimolecular system, namely, the degree of control over molecular weight was nearly ideal (for certain conditions); and molecular weights could thus be predicted by simply following general rules relating to CRP mechanisms.

This thesis presents the results of a study on the kinetics of nitroxide-mediated radical polymerization of styrene with a unimolecular initiator. The primary objective was to obtain a more comprehensive understanding of how a unimolecular-initiating system controls the polymerization process and to clarify the effects of various reaction parameters. Previous work in this field has met with some difficulties in the initiator synthesis, such as low yield and inconsistency of molecular weight. These problems were overcome by adjusting reaction conditions and procedures. Better yields of initiator with consistent molecular weight were produced by the improved methods. Control of polymerization rate and polymer molecular weight in unimolecular nitroxide-mediated radical polymerization was studied by looking at the effects of the three main factors: initiator concentration, temperature, and the initiator molecular weight on polymerization rate, molecular weight and polydispersity. Results indicated that increasing the initiator concentration had no effect on polymerization rate at low conversion, but led to lower polymerization rate at high conversion; higher initiator concentration led to lower molecular weight of the resulting polymer. It was also found that temperature significantly increased the polymerization rate, yet had no effect on number-average molecular weight, Mn, at low conversion, while it caused a plateau at high conversion levels; there was no effect on weight-average molecular weight, Mw, through the whole conversion range. In addition, increasing initiator molecular weight was found to have no effect on either polymerization rate or molecular weight. The experimental molecular weights of the unimolecular system were compared to theoretical molecular weights based on ideal controlled radical polymerization (CRP). The results were found to be close to the theoretical values. This confirmed the advantages of the unimolecular system, namely, the degree of control over molecular weight was nearly ideal (for certain conditions); and molecular weights could thus be predicted by simply following general rules relating to CRP mechanisms.

Non-point source pollution is not generated from any single source, rather can arise from a mixture of agricultural, residential, and industrial activities. As a result of these activities millions of tons of chemicals enter into aquatic environments annually with the potential to disrupt the fragile ecosystems existing within. Common anthropogenic compounds most frequently seen in estuarine environments include pesticides, antifoulants, polycyclic aromatic hydrocarbons (PAH), and industrial solvents. This dissertation examines the acute toxicity and sub-lethal effects of diuron, CuPT, B(a)P, and styrene in the mud snail, Ilyanassa obsoleta, the American oyster, Crassostrea virginica, the sea urchin, Lytechinus variegatus, and/or the barnacle, Amphibalanus (= Balanus) amphitrite. In addition, the general effects of non-point source pollution within the Rachel Carson Estuarine Research Reserve (RCERR) were examined at six sites in order to gain a better understanding of the current health of this unique habitat. Of the four compounds tested, only the industrial solvent, styrene, resulted in an LC50 (1341 µg L-1, I. obsoleta) that was within the range of currently reported environmental levels. Diuron and CuPT did not elicit mortality at environmentally relevant concentrations, but did significantly reduce fecundity in I. obsoleta and C. virginica and fertilization success and larval development in L. variegatus. The only notable sub-lethal effect elicited by the PAH, benzo(a)pyrene, was a significant decrease in egg capsule production by I. obsoleta following exposure to concentrations as low as 50 µg L-1. Within the RCERR, animals from Sites 4, 5, and 6 were observed to have significant differences with respect to fecundity, condition index, and/or ECOD activity when compared to conspecific organisms from control Site 1. This is most likely a consequence of their proximity to anthropogenic sources. Large variation in mortality (15-98.9%) was observed when families of A. amphitrite from a single population where exposed to CuPT. It is often difficult to extrapolate data from laboratory findings into natural populations. Frequently the organisms used under laboratory conditions are genetically very similar, while field population can vary with anthropogenic exposure. Caution must be taken when developing protocols for risk assessment to ensure that actual environmental conditions are being represented. / Dissertation

A fundamental kinetic model based upon the Hougen-Watson formalism was derived as a basis not only for a better understanding of the reaction behavior but also for the design and simulation of industrial reactors. Kinetic experiments were carried out using a commercial potassium-promoted iron catalyst in a tubular reactor under atmospheric pressure. Typical reaction conditions were temperature = 620oC, steam to ethylbenzene mole ratio = 11, and partial pressure of N2 diluent = 0.432 bar. Experimental data were obtained for different operating conditions, i.e., temperature, feed molar ratio of steam to ethylbenzene, styrene to ethylbenzene, and hydrogen to ethylbenzene and space time. The effluent of the reactor was analyzed on-line using two GCs. Kinetic experiments for the formation of minor by-products, i.e. phenylacetylene, α-methylstyrene, β-methylstyrene, etc, were conducted as well. The reaction conditions were: temperature = 600oC ~ 640oC, a molar ratio of steam to ethylbenzene = 6.5, and partial pressure of N2 diluent = 0.43 bar and 0.64 bar. The products were analyzed by off-line GC. The mathematical model developed for the ethylbenzene dehydrogenation consists of nonlinear simultaneous differential equations in multiple dependent variables. The parameters were estimated from the minimization of the multiresponse objective function which was performed by means of the Marquardt algorithm. All the estimated parameters satisfied the statistical tests and physicochemical criteria. The kinetic model yielded an excellent fit of the experimental data. The intrinsic kinetic parameters were used with the heterogeneous fixed bed reactor model which is explicitly accounting for the diffusional limitations inside the porous catalyst. Multi-bed industrial adiabatic reactors with axial flow and radial flow were simulated and the effect of the operating conditions on the reactor performance was investigated. The dynamic equilibrium coke content was calculated using detailed kinetic model for coke formation and gasification, which was coupled to the kinetic model for the main reactions. The calculation of the dynamic equilibrium coke content provided a crucial guideline for the selection of the steam to ethylbenzene ratio leading to optimum operating conditions.